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Disc friction of centrifugal pumps
Homola, Tomáš ; Klas, Roman (referee) ; Rudolf, Pavel (advisor)
This diploma thesis discusses the issue of the fluid flow instabilities due to rotating discs. It also deals with the calculation of axial force in centrifugal pumps and pressure distribution on cover and support disc of the impeller. Computational simulation of rotating disc is presented with the aim of capturing flow instabilities. Next computational simulation focuses on modelling a gap between the support disc (rotor) and the stator part of the pump for three different geometries, where axial force, pressure distribution on the support disc and loss torque are calculated for each of three models. Obtained results are then compared with the experiment in the conclusion
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Disc friction of centrifugal pumps
Homola, Tomáš ; Klas, Roman (referee) ; Rudolf, Pavel (advisor)
This diploma thesis discusses the issue of the fluid flow instabilities due to rotating discs. It also deals with the calculation of axial force in centrifugal pumps and pressure distribution on cover and support disc of the impeller. Computational simulation of rotating disc is presented with the aim of capturing flow instabilities. Next computational simulation focuses on modelling a gap between the support disc (rotor) and the stator part of the pump for three different geometries, where axial force, pressure distribution on the support disc and loss torque are calculated for each of three models. Obtained results are then compared with the experiment in the conclusion
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Excitation of rotating disk by stationary permanent magnets
Půst, Ladislav ; Pešek, Luděk
Abstract: Flexural vibrations of rotating disk contain forward and backward traveling waves can be excited at certain speed of rotating disk also by a standing constant single point force or by multiple points standing forces, realized e.g. by permanent magnets fixed in non-rotating space. Presented paper is contribution to the theoretical background of a new experimental excitation technique elaborated in Institute of Thermomechanics for investigation of a bladed turbine disk model with imperfection by addition several damping heads on ends of blades. Mathematical model of imperfect rotating disk was derived by using data gained experimentally and by FE computed for three lowest split modes of vibrations. It was shown how either the whole spectrum of modes of vibrations can be recorded or some resonance of selected mode can be suppressed on emphasized by means of appropriate number and positions of permanent magnets.
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ELECTROCHEMICAL DETECTOR WITH ELECTRODES ARRAY AND ROTATING DISK
SAJDLOVÁ, Zuzana
The thesis deals with the testing and optimization of hydrodynamic conditions of the electrochemical detector, which consists of a flow cell containing the electrochemical sensor with an array of electrodes. The flow cell includes a rotating disc-shaped component, which allows radial flow of analytes along the sensor electrodes. This principle imitates the rotating disk electrode, with the difference that here the electrodes are immobile. Hydrodynamic phenomena in this case are similar to RDE. Therefore, the theoretical part of my work deals with hydrodynamics and mass transfer for the well-described case of rotating disk electrode. It was found that in the current set-up under certain conditions, an analyte flowed back from the output cell channel to the sensor, even at the laminar flow. This causes a nonlinear response of the electrodes and their low reproducibility. The solution is to reduce the distance between the rotation component and the electrodes surface and reduce flow speed of analyzed liquid towards the sensor. A novel type of sensor with annular electrodes was designed and tested. It showed four times higher conversion rate of the analyte compared with the originally used AC9 electrochemical sensor having electrodes in the form of full circles lying on a circumference of a common circle. Based on calculations, conversion of the analyte on the plane electrode can be increased up to 100% when using this annular sensor, adjusting flow cell and reducing of the input flow rate. The detector was connected to the liquid chromatograph and its function was tested on two substances - ascorbic acid and dopamine. For the current detector these parameters were set: dynamic range, linearity, noise, detection limit, time constant and the temperature range at which the detector can be operated.
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